Compressor apparatus



April 8, 1930. A. BAUMANN ET AL COMPRESSOR APPARATUS Filed Feb. is, 1926Patented Apr. 8, 1930 I 7 UNITED STATES ATENT OFFICE Anon? BAU'MANN, orIBADEN, Ann ADOLF MEYER, or KUSNACHT, NEAR .zunicn,

SWITZERLAND, v

SSIGNORS TO'AKTIENGESELLSCHAFT BROWN BOVEBI & cm, or?

BAD-EN, SWITZERLAND, 'A JOINT-STOCK COMPANY or SWITZERLAND COMPRESSORAPPARATUS Application filed February 19, 1926, Serial No. 89,272, and inGermany April 6, 1925.

This invention relates to compressing apparatus in which rotarycompressors are employed for compressing a fluid medium. Its generalpurpose is the provision of an apparatus for eiiecting economy in theoperation upon an understanding of the present disclosure.

In the drawing forming a part of this speci-. fication we show onearrangement of means embodying the invention, but this is presented forpurpose of illustrationonly, as it is intended that the invention, asdefined in the claims, maybe embodied'in difierent and varying forms. Inthe drawing Fig. 1 is a diagrammatic representation of the improvedapparatus and Figs. 2 to 5 inclusive are diagrammatic rep.-

resentations of various positions of thecontrol valve. j I i There aremany kinds of service, for example,in the operation of Bessemerconverters, in which the actual employment of the compressor is requiredonly intermittently, there being, between the blast'periods, intervalsduring which thecompressor runs -light.- In

such circumstances the no-load losses. of the compressor contributeconsiderably "to the operating cost. By means of the present-invention,the no-load losses of rotary compres sors may be reduced to a minimum,either entirely without change of speed, or with only a very smallchange Described generally, the invention contemplates apparatus forclosing the compressor'on the suction and delivery sides during theno-load period and for putting it under vacuum by specialmeans.

In this way, assuming for example, that the pressure is reduced to onetenth of its original value, the no-load losses will be only 3% in steadof 30%. The plan of reducing the no load losses by closing the suctionbranch and opening the deliveryto atmosphere, sothat a sub-atmosphericpressureis produced in the V casing, is a well-known one. thissub-atmospheric pressure progressively decreases from the delivery tothe suction side of the compressor, so that, assuming a pressure ratioof 3, the average pressure would amount to approximately -=0.65 at. abs.

of the suction pressure for rotary compres- Nevertheless, Y

sors, the suction pressure willbe 0.033 at.-abs.

and the average pressure The no-load lo'sses will therefore amount toonly 0.033 30%='1% roughly. This reduction of the no-load losses ispracticable with rotary compressors in particular owing to the factthatthese losses are chiefly due to windage, which'varies as theabsolute'pressure of the enclosed medium. I

When the working conditions change at short intervals, as for example inconnection with the blast supply for Bessemer converters the vacuum mustbe created as rapidly asv possible so that the possible gain may beutilized throughout the whole period of reduced load. In such cases theproduction of the vacuum may be accelerated by connecting thecompressor, after its pressure has been reduced as much as possible bydischargingto atmosphere, to a vacuum chamber. The fur;

ther exhaustion of the compressor and chamber is carried out by means ofa vacuum pump. In order that the time taken for the further exhaustionof the compressor may'not be prolonged by the presence of the vacuum.chamber, the latter may be isolated after performing its function sothat the pump has only the contents of the compressor to remove. Duringthe periods of normal working for the compressor, the vacuum pump isconnected to thechamber so that the latter is again brought up to thefull vacuum. This accumulator arrangement possesses the advantage ofreducing the time required for exhaustion and a' further advantageinthat the pump can be run continuously, which, particularly whenchanging-over must be performed very frequently, is of great value. Thepower required by the vacuum pump itself is small. For example,supposeit is required to reduce the pressure from 0.5 to 0.1 at. abs; asthe pump is discharging to atmosphere it will have to overcome apressure ratio which varies between an m 0.5 0.1

The isothermal work of compression per 10 cubic metres of air receivedper minute will 2 and 10.

quired by the vacuum pump would amount to between only 1.5% and 1% ofthat of the main compressor. Assuming the bearing friction toremainconstant at 1%, the

total no-load losses in the above case would be 2.5% to 2%. ll ith sucha vacuum, a state of equilibrium is reached in which the leakage volumeand the capacity of the pump balance out. By means of a speciallydesigned four-way valve, also a subject of the present invention, thevarious changes described above may be performed by the operation of a.single handle, thus throwing no special clemands on the operator andpreventing mistakes in operation.

Fig. 1 shows an example of an application of the invention, in which 1may be the lowpressure stage and 2 thehigh-pressure stage of acompressor, both stages being driven from'the motor 3. The high-pressurestage 2 is required only occasionally and during I such time is isolatedfrom the pressure sys- 5, the non-return valve 6 closing automatically.By closing the valve 7 the high-pressure stage 2 is cut out, the mediumpassing from the low-pressure stage direct to the pressure pipe 5through the non-return valve'6'. The non-return valve 9 then closesautomatically so that the high pressure stage runs light. The four-wayvalve. 11 is now turned fromits initial position shown in Fig. 2,. so.that the isolated high-pressure cylinder 2 is put into communicationwith the atmosphere by way of the pipe 10 and opening 16, as in theposition shown in Fig. 3. The cylinder thus re duces its internalpressure by discharging to atmosphere, the vacuum pump 15 meanwhilebeing in communication with vacuum chamber 14 through pipes 13 and 12.On turning the valve 11 still further so that communication at 16with'the atmosphere is interrupted and the pipe 10 is connected to thevacuum chamber 14 through pipe 12, and also placed in communication withthe suction pipe 13 of the vacuum pump, as in Fig. 4, the pressure inthe high-pressure compressor is still further reduced by equalizationwith that of the vacuum chamber, and the no-load losses of the highpressure compressor correspondingly reduced. On turning the fourwayvalve 11 still further to the position shown in Fig. 5, the vacuumchamber is isolated and pipe 10 remains in communication with thesuction pipe 13 of the vacuum pump, which latter raises the vacuum inthe high pressure cylinder to the highest possible value. Owing to thefact that this cylinder was previously connected to the vacuum chamber,this is performed in a very short time. If the high pressure cylinder isto be'started up again, the four-wayvalve 11 is turned back in theopposite direction, which g operation first puts the vacuum chamber 14in communication with the pump and the high pressure cylinder, with theresult that the vacuum in the latter drops somewhat due to theequalization of pressure with that in the vacuum chamber. Afurther'movement of the four-way valve opens the compressor toatmosphere and the pressure again rises. Finallythe-opening 16 is closed(Fig.2) and the compressor returns to normal working conditions afteropening the valve 7. If the medium being compressed must not bepermit-ted to escape into the atmosphere,'the dis charge openings 16 and17 may be joined to the suction pipe 4 of the low pressure compressor1.-

The vacuum pump may be of the reciprocating, rotary, or ejector type. Itmay be so arranged that the pump is automatically shut down when thevacuum in the chamber reaches a maximum, and started up again when thevacuum falls. In this way the pump will not be running unnecessarily.

The device may be employed not only for the arrangement of compressorsshown. in

Fig. 1, but is suitable for any other arrangement desired. For example,the low pressure stage of a multi-stage compressor or one of twocompressors in parallel may be intermittently withdrawn from service andevacuated with a corresponding arrangement.

What we claim is:

1. Compressing apparatus comprising the combination with a rotarycompressor, of a vacuum chamber, meansfor closing the compressor againstinflux of air, and means for putting the compressor into communicationwith the vacuum chamber.

2. Compressor apparatus comprising the combination with a rotarycompressoryof a chamber for communication therewith, means for closingthe compressor against influx of air, means for exhausting the chamber,and means for cutting the chamber into and out of communication with thecompressor.

3. Compression apparatus comprising the combination with a rotarycompressor, of a vacuum chamber, means'for closing the compressoragainst influx of air, and means for consecutively turning thecompressor exhaust to atmosphere and connecting the compressor to thevacuum chamber.

4. Compression apparatus comprising in combination, a rotary compressor,a vacuum chamber and a vacuum pump, all arranged for communication, andmeans for placing the pump inlet into communication with the compressorand chamber selectively.

5. Compressing apparatus, comprising, in combination, a rotarycompressor, a vacuum chamber, a vacuum pump, and means for placing eachthereof into communication with either of the others selectively.

6. Compressing apparatus comprising, in combination, a rotarycompressor, a vacuum chamber, a vacuum pump, means for closing thecompressor against air influx, and means for rendering the chamber andpump efiective on the compressor. I

T. Compressing apparatus comprising, in combination, a rotarycompressor, means for closing same against influx of air, a vacuumchamber, a vacuum pump, and means for putting t-he compressor intocommunication with said other devices or atmosphere, selectively.

8. Compressor apparatus comprising, in combination, a rotary compressor,a vacuum chamber, a vacuum pump, a selectively operable valve forestablishing communication between any one of the same and any one ofthe others, and means for closing the normal inlet and outlet of thecompressor.

9. The combination with compressor apparatus and fluid-evacuating meanstherefor, of a fluid chamber; valve means having a given operatingposition providing for communication between said fluid-evacuating meansand said chamber to the exclusion of said apparatus, another operatingposition providing for communication between said apparatus and saidchamber, and still another operating position providing forcommunication between said apparatus and said fluidevacuating means tothe exclusion of said chamber; and means for actuating said valve meansto place the same in said various operating positions thereof.

10. The combination with compressor apparatus and fluid-evacuating meanstherefor, of a fluid chamber, a valvecasing having an outlet opening;valve means disposed in said casing and having various operatingpositions and being operable when in said posi tions to provide forvarious predetermined conditions of communication and non-communicationrespectively between said apparatus, said fluid-evacuating means, saidchamber and said outlet; and means for effecting movement of said valvemeans into said operating positions thereof.

11. The combination with compressor apparatus and fluid-evacuating meanstherefor, ofa fluid chamber, and single means providing for variouspredetermined conditions of communication and non-communication beoutletand independent communication between said means and said chamber, athird posltion providlng for communlcatlon between sald apparatus andsaid means and said chamber, and, a fourth position providing forcommunication between said apparatus and said means to the exclusion ofsaid chamber; and means for actuating sald valve to place the same insaid positions thereof.

In testimony whereof we have hereunto subscribed our names at Zurich,Switzerland, on the 20th day of January, A. D. 1926.

' ADOLF BAUMANN.

ADOLF MEYER.

so tween said apparatus and said fluid-evacuate

